基于滑转率的六轮纵列式月球车驱动控制研究

Study on Driving Control Method of a Six-Wheeled Tandem Lunar Rover Based on Slip Ratio

基于车轮滑转率和车轮地面力学,研究了月球车在松软月面行驶时的车轮过度下陷问题.将月球车车轮下陷和车轮—土壤作用力表达为车轮滑转率的函数,结合车辆地面力学理论并考虑纵列式车轮多通过性土壤参数的修正,建立了月球车的动力学模型.判断车轮是否发生过度下陷的标准为土壤所提供给驱动轮的土壤推力能否克服土壤对车轮的阻力.利用建立的动力学模型,计算出能够保证车轮不会过度下陷的期望滑转率.考虑到月球车动力学系统的非线性和不确定性,设计了以车轮滑转率为状态变量的滑模驱动控制器.仿真结果表明,采用该控制器可以较快地跟踪期望滑转率,避免车轮的过度滑转下陷,保证月球车能够在软质路面上正常行驶.

Based on slip ratio and terramechanics of the wheels, this paper investigates the problem of excessive sinkage of lunar rover wheel on the loose lunar soil. The sinkage of lunar rover wheel and the wheel-soil interaction forces are modeled as a function of wheel slip ratio. Dynamical model of the lunar rover is established, which incorporates the terramechanics theory and calibrats the parameters of soil by the theory of multi-pass performance of tandem wheels. Then regarding whether the effective traction force supported by the loose soil is larger than the wheel resistance, excessive sinkage of lunar rover wheel is determined. And then the desired value of wheel slip ratio is calculated by this dynamical model , which can avoid excessive sinkage of lunar rover wheel. Finally, considering the nonlinearity and uncertainty of lunar rover systems, the sliding mode controller is designed in terms of wheel slip ratio. Simulation results show that the controller effectively keeps the slip ratio of the driving wheel tracking the desired value and avoids the excessive spin and sinkage of the driving wheel, therefore guarantees the normal operation of the lunar rover on soft soil.